Overview of Windows DNA

Microsoft Windows DNA is based on a distributed system
architecture. Distributed systems contain components on more than one
computer. An Internet-based system is a typical example of a
distributed system, as it contains an application running on a client
computer (usually a browser-based application) and one or more
applications running on a Web server.

The Web server can also communicate to other servers. In this tutorial, we'll focus on
building Windows DNA systems, but the discussion is equally applicable
to other distributed systems.

One of the primary goals of distributed systems is to be highly
scalable. A highly scalable system can easily expand from thousands
of users to tens of thousands of users. Over the last two decades,
we've witnessed a steady evolution from Windows systems that can
handle a few hundred users, such as a department-size application, to
systems that can handle tens of thousands of users, such as an Internet
application. This tutorial will demonstrate how a distributed system can
be highly scalable.

Because distributed systems contain a variety of components located
on several computers, these systems are usually extremely complex.
Without a framework such as the one provided by Windows DNA, designing
and building such a system would be impossible. The Windows DNA
architecture provides two models for designing and building large,
complex distributed systems: the logical three-tier model and
the physical three-tier model. The logical three-tier model is
used to define and design the components of the system. The physical
three-tier model is used to specify the placement of these components
within the distributed system. Let's begin by looking at the
logical three-tier model.